Journal Article

The stellar mass function of the most-massive galaxies at <i>3 ≤z < 5</i> in the UKIDSS Ultra Deep Survey

K. I. Caputi, M. Cirasuolo, J. S. Dunlop, R. J. McLure, D. Farrah and O. Almaini

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 413, issue 1, pages 162-176
Published in print May 2011 | ISSN: 0035-8711
Published online April 2011 | e-ISSN: 1365-2966 | DOI:
The stellar mass function of the most-massive galaxies at 3 ≤z < 5 in the UKIDSS Ultra Deep Survey

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We have analysed a sample of 1292 4.5-μm-selected galaxies at z≥ 3, over 0.6 deg2 of the UKIRT Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS). Using photometry from the U band through 4.5 μm, we have obtained photometric redshifts and derived stellar masses for our sources. Only two of our galaxies potentially lie at z > 5. We have studied the galaxy stellar mass function at 3 ≤z < 5, based on the 1213 galaxies in our catalogue with 4.5-μm magnitudes ≤24.0. We find that (i) the number density of galaxies increased by a factor of >10 between z= 5 and 3, indicating that the assembly rate of these galaxies proceeded >20 times faster at these redshifts than at 0 < z < 2; (ii) the Schechter function slope α is significantly steeper than that displayed by the local stellar mass function, which is a consequence of both the steeper faint end and the absence of a pure exponential decline at the high-mass end; and (iii) the evolution of the comoving stellar mass density from z= 0 to 5 can be modelled as log10ρM=−(0.05 ± 0.09)z2−(0.22 ∓ 0.32)z+ 8.69. At 3 ≤z < 4, more than 30 per cent of the galaxies would be missed by optical surveys with R < 27 or z < 26. Thus, our study demonstrates the importance of deep mid-infrared surveys over large areas to perform a complete census of massive galaxies at high z and trace the early stages of massive galaxy assembly.

Keywords: galaxies: luminosity function, mass function; galaxies: statistics; infrared: galaxies

Journal Article.  11949 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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